Joel, i was going to write a proper reply for your response to my 'coconuts' post, however, time has restrained me so here is a partial reply (consider it a promisory note...).
1) Deriving 'ought' from 'is'.
First consider a logical syllogism:
Major premise: All men are mortal
Minor Premise: Socrates is a man
Conclusion: Socrates is mortal
The conclusion cannot be denied without self contradiction, it is a logical necessity.
Now, if we were to make the syllogism read:
All animals rear their young
man is an animal
therefore man ought to rear their young
then we have a conclusion that contains a copula that is not in the premesis. So the conclusion does not follow as a strict logical necessity.
OK, fine. But if you want to adopt this approach, that the first syllogism is the ONLY demonstrable truth then one must also adopt a scepticism about all the assertions of natural science. ie NO PROPOSITION ABOUT THE FUTURE FOLLOWS FROM ANY NUMBER OF PROPOSITIONS OF THE PAST (ie the problem of induction).
(You will notice that Hume, in his treatise took exactly this view, and as a result his philosophy, while acclaimed is also seen as an epistemological dead end)
Note also that a problem deriving 'is' from 'ought' does not arise if we can come to some agreement on a major premesis.
2) 'natural law'
I notice you have adopted an approach of moral pluralism. I am not sure how you can deny that this is relativistic. For it posits that there can be no 'true' moral value (At least this seems to be your thesis).
However when dealing with issues of morality, it is important to distinguish between values and beliefs. People can quite easily share common values, but seem to be in conflict, due to differing belief syst4ems.
eg. In a certain country it is considerred wrong to kill cows, no matter that the population is starving. As such they would seem to have different values from those of us who place human lives above the lives of cows. But when wee examine what their actual beliefs are, it is that they believe the souls of humans come to inhabit cows when they die. Hence to eat a cow would be to eat another person. They do not condone it, we do not condone it...
To accept that there are no objective values, is to deny the reality of human experience, the 'cry of pain' that EVERY human soul admits (to paraphrase simone weil) when some atrocity is commited against them.
Well, out of time...
Thankyou and goodnight.